1. Field of the Invention
The present invention relates to a device for total joint replacement, and more particularly to hip and shoulder joint prostheses that require less invasive surgery during installation than required by the current prostheses and methods for placement.
2. Description of the Prior Art
Arthroplasty, the restoration of normal joint motion, is frequently done by the insertion of metallic prostheses. Implant technology has improved over the last number of years and provides solutions to problems caused by injury, arthritis and other joint diseases. Frequently, the damage is sufficiently severe to require a total joint replacement. The prior art discloses numerous designs for total hip joint prosthetic devices.
Total hip joint replacements require interactive prosthetic femoral and acetabular components to emulate the ball-socket mechanism of a natural hip joint. When the supporting structure is weakened, particularly the femoral head and neck, a prosthetic femoral component with an extended shaft is implanted within the medullary cavity of the femur. Examples of this type total hip replacement prosthetic device are disclosed in U.S. Pat. No. 6,093,208 issued to Enrico Tian and U.S. Pat. No. 5,807,407 issued to England, et al. Many surgeons take this route, even when the underlying bone structure of the femoral head and neck is strong, under the theory that implantation of the shaft within the medullary cavity of the femur is required to obtain the necessary support for the prosthetic femoral head, as the femoral implant is under high stresses that can cause failure of xe2x80x9csurface replacementxe2x80x9d devices. Such failures frequently occur early in the patient""s recovery, before the bonding of the bone to the metal surfaces of the prosthetic implant has occurred. However, the insertion of the prosthetic device with a long femoral shaft requires the resection of the femoral head and neck to obtain access to the longitudinal cavity within the femur. Such surgery is very stressful to the patient and increases the risk of infection. If the device fails, any further implantation of prosthetic devices becomes exceedingly difficult, as the supporting bone structure has already been appreciably reduced.
U.S. Pat. No. 5,800,558 to Gerald A. LaHaise, Sr., U.S. Pat. No. 5,133,764 to Pappas et al., and U.S. Pat. No. 4,846,841 to Indong Oh, disclose the xe2x80x9csurface replacementxe2x80x9d technique of a total replacement of a hip joint. xe2x80x9cSurface replacementxe2x80x9d is aimed at primarily providing replacement of the joint surfaces while preserving as much of the supporting bone structure as possible and preserving the integrity of the medullary cavity. Pappas et al. ""764 and Oh ""841 each disclose a version of a cap that is implanted over the resected head of the femur. LaHaise ""558 discloses a more complex means for attaching the ball to the resected head of a femur. One advantage to the surface replacement type of total hip replacement, is that much of the femur is left intact, so that if the surface replacement method fails, it may be replaced with an intramedullary canal prosthetic component.
Each of the above patents disclose a generally solid metal acetabular cup that is fixed, usually by screws, to a prepared surface of the hip bone. An insert, a layer of plastic or metal is frequently attached to the acetabular cup, the insert being sized to receive the ball portion of the prosthetic joint that is attached to the femur.
Each of these prostheses mentioned above, are installed during lengthy, invasive, major surgery that requires surgically opening the hip area for full exposure and direct access to the hip joint. During surgery the head of the femur must be removed from the acetabular cup, for resection of the femur head or complete removal of the femur head and neck. This surgery comes at a high cost as it is complex, requiring extensive surgical support staff and operating room equipment.
Not withstanding the existence of such prior art prosthetic components and methods for attachment to the human body, it remains clear that there is a need for prosthetic components that may be inserted into the human body without a major incision gain direct access to the femur and hip bone.
The present invention relates to a prosthesis and method for implantation of that prosthesis within the human body as the replacement for a ball joint. The apparatus comprises at least one segmented shell that is attachable to the acetabulum of the hip bone of a patient. The segmented shell comprises a plurality of separate parts which may be inserted through a hole in the femur of the patient and assembled and attached to the hip bone to form a cup-shaped first shell.
A cup whose exterior is sized and configured to be received tightly within the interior of the first shell is also passed through the hole in the femur and then attached to the first shell. The interior of the cup is sized and configured to receive the ball portion of the prosthetic component.
A shaft having a first end with a ball formed thereon, that is sized and configured to be received within the cup is inserted within the hole through the femur so that the ball engages the cup for movement therein.
As the head of the femur and the acetabulum is larger than any hole that can be made through the neck of the femur, an expandable drill bit must be used to remove the head of the femur and a thin portion of the outer layer of the acetabulum.
The invention accordingly comprises an article of manufacturer possessing the features, properties, and the relation of elements which will be exemplified in the article hereinafter described, as well as the method for insertion of the article into the human body. The scope of the invention will be indicated in the claims.